The field of this invention relates to the welding of separate, coaxially located, edge abutting, metallic, cylindrical, tubular sections by the gas shielded tungsten electrode arc welding process. More particularly, the field of this invention contemplates an apparatus for automatic gas tungsten arc welding along a circumferential path thereby securing the tubular sections together forming essentially an integral, totally enclosed, tube.
The use of apparatuses to effect automatic welding of tubes has long been known. A common such apparatus is what is shown and described within U.S. Pat. No. 3,400,237, by the present inventor. The apparatus of the present invention is to employ a welding technique similar to the aforesaid Patent, and reference may be had to the aforesaid Patent for background information of the welding technique.
Previously, there have been two inherent disadvantages attributable to the tube welding apparatuses similar to the aforementioned Patent. One of these disadvantages is that, in order to establish the welding arc, it is required to apply a surge of electrical voltage. Once the arc is established, the voltage can be decreased. This surge is substantial and several times the amount of voltage that is required to maintain the arc once it is established. Because of this surge in voltage, it has not been advisable to use such tube welding equipment in conjunction with electronic equipment as the surge could easily "escape" and cause damage to the electronics within the electronic equipment.
The other disadvantage to tube welders of the aforesaid Patent is that they are limited to usage with only a close tolerance variation of size of tubing. For example, let it be assumed that the tube welder is designed to be used in conjunction with a one inch tube. This means that the welder will be able to clamp tightly onto any tube which is of a size of 0.995 inches to 1.005 inches. However, in the constructing of such tubes, it is common that one inch tubes will vary from this range of tolerances. Therefore, if a tube welder could be constructed that would easily be snugly affixable onto tubes that varied from 0.990 inches to 1.010 inches, that tube welder then would be usable in conjunction with a substantially increased number of tubes. Let it be assumed that the tube welder is to be utilized to make a thousand different welds thereby forming a thousand different tubes. If the tube welders are usable only from 0.995 to 1.005 inches, then possibly there will be two to three hundred tubes that the tube welder can not be used to effect the welding procedure. However, if the tube welder could be usable from 0.990 inches to 1.010 inches, then practically all the welds could be created.